JPH0389630A - Error correcting method - Google Patents

Abstract

PURPOSE:To correct an error even when a reception word is not in a Hamming distance (t) seen from a transmission word other than a correct transmission word by adding an error pattern at the time of the occurrence of the error of (t+1) number of or more bits larger than a maximum error correction bit number (t). CONSTITUTION:Reception bits are reproduced to a binary signal by a threshold for '0' or '1' discrimination, and tfold or less error is correctly corrected, and it is detected whether t+1 fold or more error exists or not. When the reception word is not in the Hamming distance (t) seen from another transmission word, an (t+1) bit error pattern is added to the reception word, and the number of error patterns N for syndrome '0' is obtained; and when N is one, the pattern is discriminated as the error pattern and t+1 fold error correction is performed. Since the t+1 bit error pattern is added to the reception word, t+1 fold or more error can be corrected regardless of a t fold error correction code, and the error correcting capability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an error correction method used in digital mobile radio, video compression transmission, and the like.

BACKGROUND ART In general, the minimum value of the Hamming distance between code words of an error correction code of code length n (=+m), which is obtained by adding m check bits to k bits of information bits, is defined as the minimum distance of the error correction code. Yes, if this minimum distance is 2t+l (t is a positive integer), errors of t bits or less can be correctly corrected.

Here, there are two types of code words in total, but if a sphere of radius t centered on each code word fills the n-dimensional space without any gaps, that is, if the following holds true, then this error correction code can be converted into a complete code. If 2k X

In the case of a non-perfect code, even if an error of t+1 bits or more occurs in one transmitted word, the received word will not necessarily be within the Hamming distance It from another transmitted word. In other words, a non-perfect code can not only correct an error of t bits or less, but also correct an error of t+1 bits or more without making an error correction, that is, without making an incorrect correction.
It may be possible to detect that there is an error of one or more bits.

FIG. 3 is a flowchart showing a conventional error correction method for a t-fold error correction non-perfect code.

In FIG. 3, the received transmission signal is regenerated into a binary signal by a threshold value that determines whether the received bit is rOJ or "1", and then in step 23, errors of less than 100% are correctly corrected, and the following step In No. 24, t+1 or more errors are detected.

Here, if an error greater than or equal to 0 occurs and the received word is within the Hamming distance from another transmitted word, the error is corrected in step 23, so the error is not detected in step 24. The process ends (step 26).

On the other hand, if the received word is not within the Hamming distance from some other transmitted word, it can be detected in step 24 that t+1 or more errors have occurred, and in the subsequent step 25, the received word is A flag indicating that an error is included is set, and error correction is ended (step 26).

Therefore, in the conventional example described above, errors of t bits or less can be correctly corrected, and if an error of t+1 bits or more occurs, it is possible to correctly correct errors of t+1 bits or more when the error is not within the Hamming distance from another transmitted word. It is possible to detect that an error has occurred.

Problem to be Solved by the Invention However, in the conventional error correction method described above, when an error of t+1 bits or more exceeding the maximum number of error correction bits t occurs, it is possible to detect the occurrence, but it is not possible to detect the error. The problem is that it cannot be corrected.

In view of the above-mentioned conventional problems, the present invention provides that when an error of t+1 bits or more exceeding the maximum number of error correction bits t occurs,
To provide an error correction method capable of correctly correcting an error even when a received word is not within a Hamming distance from another transmitted word that is not a correct transmitted word.

Means for Solving the Problems In order to achieve the above object, the present invention receives a non-perfect error correction encoded bit string with a code length of n bits and a maximum number of error correction bits of t bits, and generates a bit string from the received word. If an error of t+1 bits or more is detected in this error correction, an error pattern of t+i (l is a positive integer) bits is added to the received word and all patterns are corrected. It is determined whether the syndrome becomes "O" or not, and if there is one error pattern, the error pattern of the received word is corrected for t+i bits of error.

The present invention also receives a non-perfect error correction coded bit string with a code length of n bits and a maximum number of error correction bits of t bits, and sets a flag to that bit if the received bit has noise of a predetermined level or more. Then, errors of t bits or less are corrected using the syndrome generated from the received word, and if an error of t+1 bits or more is detected in this error correction, an error pattern of t+1 bits is added to the received word so that the syndrome is "0". ”, and if there is one error pattern, the error pattern of the received word is corrected for t+1 bits, and if there are two or more error patterns with the syndrome rOJ, the flag is set. The error pattern of the received word with the largest number of bits is corrected for t+1 bit errors.

With the above configuration, the present invention adds an error pattern when an error of t+1 bits or more exceeding the maximum number of error correction bits t occurs, so that the received word is within a Hamming distance from another transmitted word that is not the correct transmitted word. Errors can be correctly corrected even when they are not correct.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a flowchart showing an embodiment of the error correction method according to the present invention.

The transmission signal received in step 1 shown in FIG.
The signal is reproduced into a binary signal using a threshold value for determining ``, and in the subsequent step 3, errors of t+1 times or less are correctly corrected, and then in step 4 it is detected whether there are errors of t+1 times or more.

Here, if an error occurs on the overlay board and the received word is within the Hamming distance from another transmitted word, the error was corrected in step 3, so it is determined that there is an error in step 4. Not detected, processing ends (step 1)
1).

On the other hand, if the received word is not within the Hamming distance from another transmitted word, proceed to step 5 and initialize i (i is a positive integer) (1=1), and then proceed to step 6 to set t+i bits. error patterns are added to the received word, and the number N of error patterns for which the syndrome becomes "O" is determined.

Next, in step 7, if N22, it is not possible to determine which error pattern is the t+1 bit error pattern that occurred in the received word, so the process is terminated.Step 11) If N=1 Step 8
The pattern is determined to be an error pattern, and the tri
Perform heavy error correction. On the other hand, if N=O, the error is not t+i bits, so the process branches to step 9.

In step 9, it is determined whether I is equal to a positive integer ■ set in advance based on weight branching of code words, allowable time for correction processing, etc., and if t=1, step 1
Proceed to 0, increment i by 1, and return to step 6 to repeat the above operation. In step 9, i=1
In this case, the process ends (step 11).

Therefore, according to the above embodiment, since an error pattern of t+i bits is added to the received word, even though it is a tM error correction code, errors of t+1 or more can be corrected, improving the error correction ability. be able to.

FIG. 2 shows a second embodiment of the invention.

When a transmission signal is received in step 12, first in step 13 it is determined whether or not there is noise in the received bits that exceeds a specified value, and if there is noise, a flag is set for that bit. still. This determination is made based on whether the received bit is close to a threshold value for determining whether it is "0" or "1".

In step 15, the signal is regenerated into a binary signal using the threshold value, and in the following step 16, 12 or less errors are correctly corrected, and then in step 17, it is detected whether there are t+1 or more errors.

If t+1 or more errors are detected, proceed to step 18, add a t+1 bit error pattern to the received word,
The number N of error patterns for which the syndrome becomes "0" is determined.

If N≧2, the process proceeds to step 21, where the number of flag-set bits is counted for each t+1-bit error pattern, and the pattern with the largest number of flag-set bits is determined to be the error pattern. , t+1 times error correction.

Note that if N=1, the process proceeds to step 20, where the pattern is determined to be an error pattern, and t11 times error correction is performed.
If N=O, the process ends (step 22).

Therefore, in the above embodiment, a flag is set in advance for received bits with noise exceeding the specified value, and an error pattern of t+l bits is added to the received word. errors can be corrected, and the error correction ability can be improved.

As described in detail, the present invention provides a maximum error correction bit number t
When an error of t+1 bits or more occurs, an error pattern is added, so the error can be correctly corrected even when the received word is not within the Hamming distance from another transmitted word that is not the correct transmitted word.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing an embodiment of the error correction method according to the present invention, FIG. 2 is a flowchart showing a second embodiment of the error correction method according to the present invention, and FIG. It is a flow chart showing a correction method.

Claims (4)

[Claims] (1) Receive a non-complete error correction encoded bit string with a code length of n bits and a maximum number of error correction bits of t bits, correct errors of t bits or less using a syndrome generated from the received word, and When an error of t+1 bits or more is detected in error correction, an error pattern of t+i (i is a positive integer) bits is added to the received word and it is determined whether the syndrome becomes "0" for all patterns. , An error correction method characterized in that, when there is one error pattern, the error pattern of the received word is corrected by t+i bits. (2) The error correction method according to claim 1, wherein the i is a positive integer preset based on weight branching of code words, allowable time for correction processing, etc. (3) Receive a non-perfect error correction encoded bit string with a code length of n bits and a maximum number of error correction bits of t bits, and if the received bits have noise of a predetermined level or more, set a flag on that bit, Errors of t bits or less are corrected using the syndrome generated from the received word, and if an error of t+1 bits or more is detected in the error correction, an error pattern of t+1 bits is added to the received word and the syndrome is set to "0". If there is one error pattern, correct the error pattern of the received word by t+1 bits, and if there are two or more error patterns that result in a syndrome of "0", the flag is set. An error correction method characterized in that the error pattern of a received word having the largest number of bits is corrected for t+1 bits. (4) The method according to claim (3), characterized in that it is determined whether or not the received bits have noise of a predetermined level or more based on whether the received bits are close to a threshold value for determining whether the received bits are "0" or "1". Error correction method.